Authentication using digital certificates and public/private key pairs has gained wide popularity in a variety of applications. In a public/private key cryptographic application, digital content may be encrypted using a public key. Only a user or device in possession of the corresponding private key may decrypt the resulting encrypted digital content. Authentication between users and/or devices may also be achieved using public/private key pairs using well-known challenge and response techniques. Private keys may be stored on devices utilizing public/private key cryptography for authentication and encryption/decryption of digital content.
Digital content protection schemes have been implemented in consumer electronics devices to provide copy protection of digital audio and video content. For example, High-bandwidth Digital Content Protection (HDCP), developed by Intel Corporation, prevents copying of digital audio and video content as it travels across High-Definition Multimedia Interface (HDMI), Digital Visual Interface (DVI), DisplayPort, Gigabit Video Interface (GVI), or Unified Display Interface (UDI) connections. Implementing HDCP requires a license from Digital Content Protection, LLP (a subsidiary of Intel). The HDCP scheme involves three basic processes to achieve various goals as listed below:
1. authentication: authentication of devices prevents non-licensed devices from receiving content;
2. encryption: encryption of the content data stream prevents eavesdropping; and
3. key revocation: key revocation processes ensure that devices that have been compromised and/or cloned can be blocked from receiving content.
The HDCP scheme therefore requires the use of public keys and certificates issued by DCP as well as secret device keys. Each HDCP-capable device has a unique set of keys. Device keys are exchanged during authentication. Also, keys are shared to encrypt and decrypt content.
There are three types of devices that may use HDCP. Each device contains one or more HDCP transmitters and/or receivers. Sources send content to be displayed. Examples of sources include DVD players, BIu-ray players, set-top boxes, gaming consoles, and computer video cards. Sources have one or more HDCP transmitters Sinks render the content for display and cannot transmit content to other devices. Sinks therefore have only receivers. Examples of sinks include HDTV s and LCD monitors. Repeaters accept content, decrypt it, then re-encrypt and retransmit the data. Repeaters have both receivers and transmitters. An example of a repeater is an A/V receiver.
FIG. 1A illustrates a simple home-theater arrangement utilizing High-bandwidth Digital Content Protection (HDCP) over a traditional wired connection. As shown, system 10 comprises a source 100 and a sink 104, coupled by HDMI connection 102. Source 100 (shown here as a DVD player) includes device-specific HDCP keys, which may be stored in an HDMI chip on the device. Sink 104 (shown here as an LCD TV) includes device-specific HDCP keys, which may be stored in an HDMI chip on the device. Key exchange occurs over the HDMI connection 102 and encrypted content travels across this connection.
The desire to allow consumers to connect displays, devices, and home-theater equipment using standard protocols and interfaces such as TCP/IP, WiFi, USB, and Wireless Home Digital Interface (WHDI) has led to revisions of the HDCP standard specifications. HDCP revision 2.0 defines an interoperable method for supporting such emerging usage models.
FIG. 1B illustrates a home-theater arrangement utilizing HDCP 2.0 over a wireless network. As shown, system 12 comprises a source 120 and multiple sinks 124a, 124b, and 124c. Source 100 (shown here as a DVD player) transmits content to sinks 124a, 124b, and 124c (shown here as HDTVs) over wireless network connections 122a, 122b, and 122c (not labeled). Key exchange occurs over wireless network connections 122a, 122b, and 122c and encrypted content travels across these connections. Each of the devices 120, 124a, 124b, and 124c includes device-specific HDCP keys that may be stored on the device.
FIG. 1C illustrates a home-theater arrangement utilizing HDCP 2.0 over a wireless network. As shown, system 14 comprises multiple sources 140a, 140b, and 140c and sink 144. Sources 140a, 140b, and 140c (shown here as a DVD player, a gaming console, and a notebook computer) transmit content to sink 144 (shown here as a HDTV) over wireless network connections 142a, 142b, and 142c (not labeled). Key exchange occurs over wireless network connections 142a, 142b, and 142c and encrypted content travels across these connections. Each of the devices 120a, 120b, 120c and 124 includes device-specific HDCP keys that may be stored on the device.
FIG. 1D illustrates a home-theater arrangement utilizing HDCP 2.0 over a mixed network including wired connections and wireless connections. As shown, system 16 comprises source 160, converter/repeater 166, and sink 164. Source 160 (shown here as a DVD player) transmits content to converter repeater 166 (shown here as an A/V receiver) over TCP/IP connection 162. Converter/repeater 166 decrypts content received from source 160, re-encrypts it, retransmits to sink 164 over wireless network connection 168 (not labeled), and also performs protocol conversions. Key exchange occurs between source 160 and converter/repeater 166 over TCP/IP connection 162 and encrypted content travels across this connection. Key exchange occurs between converter/repeater 166 and sink 164 over wireless network connection 168 and encrypted content travels across this connection. Each of the devices 160, 164, and 166 includes device-specific HDCP keys that may be stored on the device.
In all scenarios depicted in FIGS. 1A-1D, security of the device-specific secret keys is paramount. There are two basic security concerns: (1) protecting device-specific secret keys during incorporation into a device or system (i.e., during device manufacturing and production), and (2) protecting the device-specific secret keys for use during transmission and reception of HDCP-protected content. Thus there is a need for a solution to address both of these security concerns.